A130451 Number of divisors of A123193(n).

1, 2, 2, 3, 2, 2, 3, 2, 2, 5, 2, 2, 2, 8, 3, 2, 8, 2, 2, 8, 2, 8, 2, 2, 3, 2, 8, 8, 2, 2, 8, 2, 8, 2, 2, 8, 2, 5, 2, 8, 2, 2, 2, 8, 2, 8, 8, 2, 2, 8, 2, 8, 3, 2, 8, 8, 2, 8, 8, 2, 8, 2, 2, 2, 8, 8, 2, 2, 8, 2, 3, 8, 2, 8, 2, 2, 8, 8, 8, 8

Offset: 1

Author

Giovanni Teofilatto, Aug 08 2007

Keywords

• easy
• nonn

Programs

Maple

isFib := proc(n) local i ; for i from 1 do if combinat[fibonacci](i) > n then RETURN(false) ; elif combinat[fibonacci](i) = n then RETURN(true) ; fi ; od: end: A123193 := proc(n) option remember ; local nmin,k ; nmin := 1 : if n > 1 then nmin := A123193(n-1)+1 ; fi ; for k from nmin do if isFib( numtheory[tau](k) ) then RETURN(k) ; fi ; od: end: A130451 := proc(n) numtheory[tau](A123193(n)) ; end: seq(A130451(n),n=1..80) ; # R. J. Mathar, Nov 16 2007

Mathematica

FibQ[n_] := IntegerQ[Sqrt[5 n^2 + 4]] || IntegerQ[Sqrt[5 n^2 - 4]];
Select[DivisorSigma[0, Range[250]], FibQ] (* Jean-François Alcover, Jan 27 2024 *)

Formula

a(n)=A000005(A123193(n)). - R. J. Mathar, Nov 16 2007

Extensions

Corrected and extended by R. J. Mathar, Nov 16 2007